Alarm systems



July 1, 1969 I 41. w. WINDER 3,453,499

I ALARM SYSTEMS Filed F915. 23, 1967 7 Sheet 2 of 4- IE E T .I' (I) NO MONITORING CONTACTS 5 F I6. 40 INVENTOR.

BY JAMES]? WINOER TTORNEY J. w. WINDER ALARM SYSTEMS July 1, 1969 Sheet 3 of 4 Filed Feb. "23. 1967 FIG. 4b

NC MONITORING CONTACTS INVENTOR.

BYl

JAMES W. WINDER XTTORNEY United States Patent C) 3,453,499 ALARM SYSTEMS James W. Winder, Boothwyn, Pa., assignor to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey Filed Feb. 23. 1967, Ser. No. 617,911 Int. Cl. H02]: 1/04; Hlh 47/22 US. Cl. 317-113 16 Claims ABSTRACT OF THE DISCLOSURE This invention relates to alarm systems, and more particularly to a relay unit of the plug-in type and a flasher unit of the plug-in type usable in such systems.

For monitoring certain equipment (e.g., pump motors. valves, etc.) so as to provide normal and off normal indications, there has previously been developed a certain type of alarm apparatus which is used rather extensively in the process industries. Such apparatus includes a relay circuit or unit mounted inside a can which plugs into a socket mounted on a control panel, the relay unit functioning to operate a flasher unit and an alarm (e.g., a buzzer or horn) when an off normal condition exists in the equipment being monitored. Ordinarily, one flasher unit is used for several relay cans.

Depending upon the type of equipment being monitored, as Well as upon the particular condition being monitored, the off normal alarm has to be given for one or the other of two different types or modes of operation of the condition-responsive elements. In one of these two types or modes of operation (which will herein be designated as the normally open or NO mode), the off normal alarm has to be given when normally open condition-responsive contacts in the monitored equipment close; in the other type or mode (which will herein be designated as the normally closed or NC mode), the off normal alarm has to be given when normally closed condition-responsive contacts in the monitored equipment open.

According to the prior art, unlike (i.e., differently wired, internally) relay cans had to be used for the NO and NC modes, and also, the sockets (on the control panel) had to be wired differently for these two different types of relay cans. Also, if the flasher unit were of the plug-in type (which is almost always the case), the socket for this latter unit would generally have to be wired differently from the sockets for the relay cans.

The necessity of stocking and selectively utilizing two different types of relay cans, together with the necessity of utilizing two different socket wiring arrangements, tends to make the alarm system of the prior art inconvenient to use, as well as expensive.

An object of this invention is to provide in an alarm system a single, universal type of relay can circuit which may be used for either the NO mode or the NC mode of operation.

Another object is to provide in an alarm system a socket circuit which, applied to a symmetrical socket for a plug-in relay can, may be utilized for either an NO or an NC mode of operation.

A further object is to provide in an alarm system a plug-in relay can circuit which, in conjunction with a symmetrical socket, may be changed from the NO mode to the NC mode of operation, and vice versa, merely by reversing the relay can in the socket.

A still further object is to provide in an alarm system a socket circuit which may be used for either a plug-in flasher unit or a plug-in relay can.

The foregoing and other objects of the invention are accomplished, briefly, in the following manner: A symmetrical socket can accommodate a plug-in type relay can in one or the other of two opposite positions at will, these positions being differentiated from each other by a plug rotation of one of these two positions being utilized for an NO mode of operation of the can and the other for an NC mode of operation. The conditionresponsive contacts in the monitored equipment are connected to the socket, the NO mode of operation of the can being utilized when these contacts are of the NO type and the NC mode of operation of the can being utilized when these contacts are of the NC type. In the relay can, two relays are connected into separate circuits in such a manner that one of the relays is energized for both normal and off normal" conditions of the condition-responsive contacts, regardless of which mode of operation is being used; for the normal condition of the condition-responsive contacts, the other relay is unenergized for the NO mode and energized for the NC mode, this other relay being reversed (from its normal condition) in both modes for the off normal condition of the condition-responsive contacts. When this last-mentioned relay reverses for off normal, a red light is made to flash on and off and a horn or buzzer is sounded. A plurality of symmetrical sockets, all exactly alike in construction and all wired the same, are provided on a control panel for accommodating the relay cans in the appropriate one of the two different positions, and any one of these sockets can accommodate a plug-in type flasher unit. A lamp test switch and circuit are provided for testing the operation of the signal lamps, when desired. A manually-operated lock-in circuit is provided for each socket, and it may be utilized when desired, to enable the relay cans to be used with condition-responsive contacts which are opened or closed only momentarily when an off normal condition arises; these lock-in circuits would not ordinarily be used with condition-responsive contacts which are maintained opened or closed when their off normal condition arises.

A detailed description of the invention follows, taken conjunction with the accompanying drawings, wherein: FIG. '1 is a face view of a receptacle;

FIGS. 2 and 3 are diagrammatic representations of plugs;

FIG. 4 (constituted by FIG. 4a and 4b, together) is a circuit diagram of two relay units with plugs and sockets according to the invention;

FIG. 5 is a circuit diagram of a flasher unit according to the invention; and

FIGS. 6 and 7 are views of opposite faces of a mask utilized in the invention.

Refer first to FIGS. 1-3. A symmetrical socket or re ceptacle 1, viewed from the front in FIG. 1, has twentyfi've pin-receiving jacks or openings arranged in a symmetrical pattern in a body of insulating material; these jacks are denoted by the letters A through Y, inclusive. In addition to the twenty-five jacks mentioned, socket 1 has four grounded pin-receiving jacks G1, G2, G3, and G4 which are located eccentrically of the socket, i.e., in off-center fashion. These latter jacks are used for locating purposes, and will be referred to more fully hereinafter.

For an alarm system, a plurality of sockets 1 are mounted on a control panel, one socket for each of the items to be monitored plus one socket for each of the flasher units to be used. All of these sockets are wired in exactly the same manner.

A relay circuit or unit, mounted inside a can and termed herein for convenience a relay can or an alarm can, can be plugged into each of the sockets 1 which represents an item to be monitored. Each of the items to be monitored (such as pump motors, valves, etc.) has a pair of monitoring contacts which reverses its sense when the item changes from a normal to an off normal condition. The monitoring contacts are of course condition-responsive contacts. These monitoring contacts operate in either one or the other of two different modes. In one of these (herein termed the normally open or NO mode), the contacts are open for the normal condition, and are closedwfor the off norma condition. In the other (herein termed the normally closed or NC mode), the contacts are closed for the normal condition, and are open for the ofi normal condition. At first glance, it would seem that these two modes of operation are diametrically opposite or inconsistent, so that it would appear necessary to use entirely different types of relay cans for these different modes of operation; in fact, according to the prior art, this was necessary. However, this invention enables identical relay cans to be used for either mode of operation, in a selective manner, and this merely by inserting the plug of the relay can into the symmetrical socket 1 in one orientation or the other, one of these orientations being differentiated from the other by :a 180 rotation of the plug.

The two orientations just referred to are illustrated in FIGS. 2 and 3. FIG. 2 represents the back view of a relay can" plug oriented so that the relay can functions in the NO mode. Since FIG. 2 is a view of the plug from the rear, and FIG. 1 is a view of the receptacle or socket from the front, a superposition of FIG. 2 on FIG. 1 indicates how the twenty-five contact pins of plug 2 fit into the twenty-five jacks of socket 1, for the NO mode. Plug 2 has tWo locating pins G1 and G2 which, in the NO position of the plug, fit into the two locating jacks G1 and G2, respectively, of socket 1.

FIG. 3 represents the back view of a relay can" plug oriented so that the relay can functions in the NC mode. A superposition of FIG. 3 on FIG. 1 indicates how the twenty-five contact pins of plug 2 fit into the twentyfive jacks of socket 1, for the NC mode. In the NC position of the plug 2, the locating pins G1 and G2 carried thereby fit into the two locating jacks G3 and G4, respectively, of socket 1.

Refer now to FIGS. 4a and 4b, which is a circuit diagram of the circuitry utilized for the symmetrical sockets 1 and also for the relay cans and their plugs 2. In FIG. 4a, the universal-type relay can of this invention is illustrated as being plugged in for operation in the NO mode, and in FIG. 4b, the can is illustrated as being plugged in for operation in the NC mode.

Although it is theoretically possible for certain portions of the relay circuitry to operate satisfactorily on alternating electrical current, direct current operation is preferred. To supply this direct current, the commercial alternating current power source 3 has its voltage changed to a suitable value by means of an adjustable auto-transformer 4, this changed voltage then being rectified (converted to direct current) by means of a full-wave bridge rectifier 5 of conventional type. The positive output terminal of rectifier 5 is connected to a positive power bus 6, and the negative output terminal of rectifier 5 is connected to a negative power bus 7. For convenience in illustration, the positive bus 6 and the negative bus 7 appear at both the top and bottom of FIGS. 4a and 4b. Also, the symmetrical socket 1 is split up into two portions, an upper portion 1a and a lower portion 1b; similarly, the plug 2 is separated into two portions, an upper fie-fin on and a lnwpr nn-rtinn 2h,

The relay can is denoted generally by numeral 8. Reference will first be made to FIG. 4a, and the NO mode of operation will be first exclusively described. The NO monitoring contacts 9 (condition-responsive contacts) are associated with equipment being monitored, these contacts being open in response to a normal" condition of the equipment and being closed in response to an off norma condition. The contacts 9, when closed, supply power to the winding 10 of a relay 11 which is mounted within can 8, by way of a circuit as follows: positive bus 6, contacts 9, socket jack V, plug pin V, relay winding 10, plug pin M, socket jack M, negative bus 7. Thus when an off normal condition occurs contacts 9 close and relay 11 is energized; for a normal condition, contacts 9 are open and relay 11 is unenergized. Relay 11 is illustrated in the unenergized condition in FIG. 4a.

A second relay 12 having a winding .13 is also mounted within can 8. Relay 12 is energized under normal condition (it is illustrated in the energized condition in FIG. 4a), by way of a circuit as follows: positive bus 6, a normally-closed, single pole, pushbutton silence switch 14, socket jack W, plug pin W, the normally-closed contacts 15 of relay 11, relay winding 13 plug pin M, socket jack M, negative bus 7. Once energized thusly, relay 12 is sealed in (maintained energized) through the following circuit: positive bus 6, switch 14, socket jack R, plug pin R, the normally-open (but now closed) contacts 16 of relay 12, relay winding 13, pin M, jack M, negative bus 7.

When the condition being monitored is normal, a green signal lamp 17 is energized through the following circuit: positive bus 6, socket jack U, plug pin U, the normally-closed contacts 18 of relay 11, plug pin P, socket jack P, lamp 17, negative bus 7.

Under condition normal, the operation of the red signal lamp 19 (which is the alarm lamp, as will become apparent hereinafter) may be tested by operation of a momentary-contact, single pole, normally-open pushbutton test switch 20. The closing of switch 20 completes an energization circuit for lamp 19, as follows: positive bus 6, switch 20, socket jack E, plug pin E, diode 21, the normally-closed contacts 22 of relay 11, plug pin G, socket jack G, lamp 19, negative bus 7.

It has previously been described how relay 11 is pulled up or energized when contacts 9 close, in response to an off normal condition of the equipment being monitored. This is the operation that takes place with monitoring contacts which are maintained in one position or the other, such as auxiliary contacts in a controller for an electric motor. A lock-in switch 24 (which may be a single pole, double throw switch) is provided, to enable operation of the alarm circuit of this invention with monitoring contacts which are opened or closed only momentarily. In the previously-described operation (for maintained contacts at 9), this lock-in switch would be in the off position illustrated in FIG. 4a. When the lock-in switch 24 is on, once relay 11 is energized (even only momentarily) as a result of the closing of contacts 9, this relay is sealed in (or locked in) by a circuit as follows: positive bus 6, socket jack U, plug pin U, plug pin X, socket jack X, switch 24 (now 011 its on contact), socket jack K, plug pin K, the normally-open (but now closed) contacts 25 of relay 12, the normally-open (but now closed) contacts 26 of relay 11, winding 10, plug pin M, socket jack M, negative bus 7.

An example of momentary monitoring contacts might be contacts on a relay of a photoelectric device, which latter operates when some object breaks a beam of light; in this instance, switch 24 would be on.

Another instance in which the lock-in switch feature may be used (i.e., switch 24 being on) is the case wherein the monitoring contacts are in a pressure, flow, or level operated device. It is entirely possible for these instruments to be at a point just ready to give an alarm; then, pulsations in pressure or flow, or agitation of the liquid level, may give intermittent alarms. This may be annoying to an operator, because the alarm may come on and go off so fast that he cannot see which indicating lamp flashed on. With the lock-in switch 24 on, the alarm clocks in (i.e., relay 11 locks up) even on a single pulse (as produced by the closing of contacts 9), enabling the operator to readily determine which device is giving an alarm.

Because the lock-in feature is controlled by a switch 24, an operator who wishes to have an alarm lock in can make the change himself.

When relay 11 is energized upon the occurrence of an off normal condition (due to the closing of contacts 9), a connection'is made to a bus 27 from positive bus 6, to energize bus 27 from bus 6. The aforesaid connection may be traced as follows: positive bus 6, socket jack U, plug pin U, diode 28, the normally-open (but now closed) contacts 29 of relay 11, diode 30, the normallyopen (but now closed) contacts 31 of relay 12, plug pin Y, socket jack Y, bus 27. When bus 27 is thus energized positively, current flows through the winding 32 of horn relay 33 to negative bus 7, energizing this horn relay to close its normally-open contacts 34. Contacts 34 being connected in series with horn 35 between positive bus 6 and negative bus 7, horn 35 is energized to sound the same when an off normal condition appears.

Horn 35 may be deenergized, to silence or acknowledge the alrm, by pressing the silence switch 14 to open position to deenergize relay 12, opening its contacts 31 to deenergize horn relay 33 (by deenergizing bus 27). This opens the horn-energizing contacts 34, silencing the horn. It may be noted here that relay 12 is not reenergized when switch 14 is released (or reclosed), because relay 11 is now energized (opening its contacts 15), and the opening of contacts 16 opens the sealing-in circuit of relay 12.

The positive energization of bus 27 in response to an off normal condition results in thhe giving of another type of alarm indication. This will now be detailed.

Refer now to FIG. 5. A flasher unit is mounted inside a plug-in type of can denoted generally by numeral 36. The flasher unit includes a plug 2a-2b similar to that previously described in connection with the relay can," which plugs into the same type of symmetrical socket 1a-1b as previously described. The insertion of the flasher unit plug into its socket is made in the same manner as that previously described for a relay can operating in the NO mode, which is illustrated in FIG. 4a.

The flasher unit 36 is energized from the positivelyenergized bus 27 under off normal conditions; the flasher relay 37 is energized from bus 27, through socket jack Y, plug pin Y, winding 38 of relay 37, plug pin M, socket jack M, to negative bus 7. Relay 37 has two sets of normally-open contacts 39 and 40. When closed, contacts 39 serve to provide a circuit path for coupling the positive bus 6 to a bus 41, via socket jack U, plug pin U, the intermittenly-operated contact 42 of a single-pole, double-throw type of contact, contacts 39, plug pin A, socket jack A, bus 31. The intermittently-operated contact 42 serves to place a pulsating energization signal on bus 41, the energization being applied to bus 41 when contact 42 is closed.

When closed contacts serve to energize a flasher motor 43, via a circuit which may be traced as follows: positive bus 6, socket jack U, plug pin U, contacts 40, motor 43, plug pin M, socket jack M, negative bus 7.

The flasher motor 43 operates or drives the moving contact arm 45 of a contact arrangement 44, which is equivalent to a single-pole, double-throw arrangement. Arm 45, when driven, alternates between fixed contacts 42 and 46; when contact 42 is closed, contact 46 must be open. Since arm 45 is connected via plug and socket connector U to positive bus 6, and since contact 42 is connected via relay contacts 39 (now closed) and plug and socket connector A to bus 41, it may be seen that whenever contact 42 is closed, a positive energization signal is placed on bus 41; under otf normal or alarm conditions, a pulsating signal is placed on bus 41 because flasher motor 43 is then energized to intermittently close arm 45 on contact 42.

Contact 46, connected to the high side of flasher motor 43, is used to ensure that this motor always stops with contact 42 closed. Thus, when the silence or acknowledge switch 14 is pressed to deenergize relay 12, thus deenergizing bus 27 and relay 37, one energization circuit for motor 43 is broken. However, if at this time arm 45 is on contact 46, motor 43 is energized from positive bus 6 via plug and socket connector U, arm 45, and contact 46. Thus, motor 43 will continue to rotate until arm 45 is on contact 42. This means that when relay 37 is next energized to turn on flasher motor 43, the first cycle of pulsating signal on bus 41 will be the on cycle.

As previously described, the occurrence of an off normal condition results in the closing of contacts 9, energizing relay 11, which energizes bus 27. Flasher relay 37 is then energized to turn on flasher motor 43, placing a pulsating positive signal on bus 41. (It will be remembered that horn 35 is also energized as a result of the energization of bus 27.)

The pulsating positive signal is fed from bus 41 through socket jack A, plug pin A, the normally-open (but now closed) contacts 47 of relay 12, the normallyopen (but now closed) contacts 48 of relay 11, plug pin G, socket jack G, and the red lamp 19, to negative bus 7. This causes the red lamp 19 to flash on and olf, the particular red lamp which is flashing, of course, indicating which particular one of the various items being monitored (in the example, this would be the one associated with contacts '9) is off normal.

As previously mentioned, the alarm is acknowledged by pressing the silence or acknowledge switch 14, opening the same and deenergizing relay 12. (This silences horn 35, as previously described.) The resultant opening of contacts 31 of relay 12 removes the energization voltage from bus 27, deenergizing the flasher relay 37, which turns oil the flasher motor 43. The open-ing of contacts 47 of relay 12 breaks the flasher circuit from bus 41 to red lamp 19.

When relay 12 is deenergized by the acknowledgement, its normally-closed contacts 49 close. This completes a steady (non-flashing) energization circuit for red lamp 19, as follows: positive bus 6, socket jack U, plug pin U, diode 28, the normally-open (but now closed) contacts 29 of relay 11, the normally-closed contacts 49 of relay 12, plug pin G, socket jack G, red lamp 19, negative bus 7. The red lamp 19 will thus be on steadily at this time.

If there is an off normal condition (resulting in the red lamp 19 being on) when it is desired to test the lamps, the operation of the green signal lamp 17 may be tested by operation of test switch 20. In this case, the closing of switch 20 will complete an energization circuit for lamp 17, as follows: positive bus 6, switch 20, socket jack E, plug pin E, the normally-open (but now closed) contacts 50 of relay 11, plug pin P, socket jack P, lamp 17, negative bus 7.

Up to this point, the detailed description has described the operation of the relay can arrangement when the same is operating in the NO mode. This is depicted in FIG. 4a. The operation of the relay can arrangement when the same is operating in the NC mode will now be described. In FIG. 4b, the can 8 is illustrated as being plugged into the socket 1 for operation in the NC mode. This corresponds to a superposition of FIG. 3 on FIG. 1, and the plug and socket connections are denoted accordingly in FIG. 4b.

The NC monitoring contacts 51 (condition responsive contacts) are associated with equipment being monitored, these contacts being closed in response to a norma condition of the equipment and being open in response to an off normal condition. The NC contacts 51 supply power to winding 10 of relay 11, by way of a circuit as follows: positive bus 6, contacts 51, socket jack V, plug pin D, plug pin B, socket jack X, lock-in switch 24 (assumed to be in the off position as illustrated), socket jack Q, plug pin I, winding 10 of relay 11, plug pin M, socket jack M, negative bus 7. Thus, for a normal condition, relay 11 is energized because contacts 51 are closed; when an off normal condition occurs, contacts 51 open and relay 11 is deenergized. Relay 11 is illustrated in the energized condition in FIG. 4b.

Relay 12 is again energized under normal condition, by way of a circuit as follows: positive bus 6, the normally-closed silence switch 14, socket jack W, plug pin C, the normally-open (but now closed) contacts 52 of relay 11, winding 13 of relay 12, plug pin M, socket jack M, negative bus 7. Once energized thusly, relay 12 is sealed in through the following circuit: positive bus 6, switch 14, socket jack R, plug pin H, the normally-open (but now closed) contacts 16 of relay 12, relay winding 13, pin M, jack M, negative bus 7.

When the condition being monitored is normal, green lamp 17' is energized through a circuit as follows: positive bus 6, jack U, pin E, the normally-open (but now closed) contacts 50 of relay 11, pin P, jack I, lamp 17, negative bus 7.

Under normal condition, the red lamp 19' may be tested by operation of test switch 20; the closing of this switch completes an energization circuit for lamp 19, as follows: positive bus 6, switch 20, jack E, pin U, diode 28, the normally-open (but now closed) contacts 29 of relay 11, pin S, jack G, lamp 19, negative bus 7.

Assume now that the lock-in switch 24 for the NC mode (FIG. 4b) is on. Under normal condition, when the power is turned on relay 12 is unenergized, and cannot be energized instantaneously because relay 11 is also unnenergized, and its contacts 52 are open. When relay 12 is unenergized, its normally-closed contacts 53 are closed. Hence, relay 11 will be energized as soon as the power is applied, through a circuit as follows: positive bus 6, closed contacts 51, jack V, pin D, pin B, jack X, switch 24 (now on its on contact), jack K, pin 0, closed contacts 53, winding 10 of relay 11, pin M, jack M, negative bus 7. When relay 11 is energized, its normally-open contacts 52 close. This causes relay 12 to be energized immediately after relay 11 is energized, through the following circuit: positive bus 6, closed switch 14, jack W, pin C, closed contacts 52, winding 13 of relay 12, pin M, jack M, negative bus 7.

If there were an alarm or off norma condition at the time the power is turned on, contacts 51 would be open, so that relay 11 could not be energized. Relay 12 also could not be energized, in this case. However, the indicating lamps would indicate this off normal condition; the indication would be off normal, acknowledge, which would be a proper indication in this case. This will become more completely understood hereinafter.

In the NC mode, when the lock-in switch 24 is on," there are two parallel circuit paths from the on terminal of this switch (which latter is now connected through contacts 51 to positive bus 6, via jack V, pin D, pin B, and jack X) to the upper end of winding 10 of relay 11. One of these two last-mentioned circuit paths is through jack K, pin 0, and contacts 53 of relay 12; the other is through jack L, pin N, and contacts 26 of relay 11. If the condition is normal, contacts 53 would be open (relay 12 being energized as illustrated), but contacts 26 would be closed (relay 11 being energized as illustrated), sealing in relay 11 through the following circuit: positive bus 6, contacts 51, jack V, pin D, pin B, jack X, switch 24 (now on its on contact), jack L, pin N, closed contacts 26, winding 10, pin M, jack M, negative bus 7. Now, if the NC monitoring contacts 51 open in response to an off norma condition, even though this opening be only momentary, relay 11 is deenergized (as previously mentioned), and this relay is locked out by the opening of its contacts 26 (contacts 53 remaining open). Relay 11 can only be reenergized by pressing the acknowledge button 14, which deenergizes relay 12; the deenergization of the latter closes its contacts 53 and establishes an energization circuit for relay winding 10 through these contacts. Thus, in the NC mode, the lockin switch 24 really serves as a lock-out switch.

When relay 11 is deenergized upon the occurrence of an 01f normal" condition (due to the opening of contacts 51), a connection is made to bus 27 from positive bus 6; this connection may be traced as follows: positive bus 6, jack U, pin E, diode 21, normally-closed contacts 22 of relay 11, diode 54, the normally-open (but now closed) contacts 47 of relay 12, pin A, jack Y, bus 27. As previously described, when bus 27 is energized positively, horn relay 33 is energized to sound horn 35. The acknowledge or silence switch 14 is pressed to deenergize relay 12, thereby to deenergize bus 27. It may be noted here that relay 12 is not reenergized when switch 14 is released (or reclosed), because relay 11 is now deenergized (opening its contacts 52), and the opening of contacts 16 opens the sealing-in circuit of relay 12.

As previously described in connection with FIG. 5, the positive energization of bus 27 in response to an elf normal condition results in the energization of flasher unit 36 (which may be used in conjunction with two or more relay cans such as the two shown in FIGS. 4a and 4b), and when this flasher unit is energized a pulsating positive energization signal is placed on bus 41. The pulsating positive signal is fed from bus 41 through jack A, pin Y, the normally-open (but now closed) contacts 31 of relay 12, the normally-closed contacts 55 of relay 11, pin S, jack G, and the red lamp 19', to negative bus 7. This causes the red lamp to flash on and off.

In the NC mode, just as in the NO mode previously described, the alarm is acknowledged by pressing (opening) the switch 14, which causes deenergization of relay 12. The resultant opening of contacts 47 of relay 12 removes the energization voltage from bus 27, deenergizing the flasher relay 37. The opening of contacts 31 of relay 12 breaks the flasher circuit from bus 41 to red lamp 19'.

The deenergization of relay 12 in response to the acknowledgement sets up a non-flashing energization circuit for red lamp 19', as follows: positive bus 6, jack U, pin E, diode 21, the normally-closed contacts 22 of relay 11, the normally-closed contacts 49 of relay 12, pin S, jack G, red lamp 19', negative bus 7. In this last case, then (NC mode, condition 01f normal, acknowledged), the red lamp will be steadily on.

If there is an olf normal condition (resulting in the red lamp 19 being on) when it is desired to test the lamps, the operation of the green signal lamp 17 may be tested by operation of test switch 20. The closing of switch 20 will complete an energization circuit for lamp 17, as follows: positive bus 6, switch 20, jack E, pin U, the normally-open (but now closed) contacts 18 of relay 11, pin P, jack J, lamp 17', negative bus 7.

As previously described, FIG. 2 represents the plug 2 of a relay can 8 oriented with respect to the socket 1 (FIG. 1) in such a manner that, when the FIG. 2 plug is inserted into the symmetrical socket, the corresponding relay can will function in the NO mode, as depicted in FIG. 4a. FIG. 3 represents a plug orientation such that when this latter plug is inserted into the symmetrical socket, the corresponding relay can will function in the NC mode, as depicted in FIG. 4b.

A reversible mask 56, made of insulating material and opposite faces of which are represented in FIGS. 6 and 7, respectively, may be placed over the socket 1, to make sure that the relay can is .plugged into the socket properly to function in the particular mode desired. The

mask 56 has an outer configuration matching that of socket 1, and has a square central aperture 57 sized to allow the passage therethrough of the twenty-five pins A through Y of plug 2. Alternatively, instead of the single large aperture 57, twenty-five spaced holes could be provided in the central area of mask 56, one hole for each of the twenty-five socket jacks A through Y of socket 1.

In addition to the aperture 57, mask 56 has therein two off-center or eccentrically-located holes 58 and 59 which are sized to allow free passage therethrough of the grounded locating pins G1 and G2, respectively, of plug 2. Holes 58 and 59 are arranged in such a way that when the NO face of mask 56 is uppermost (as illustrated in FIG. 6, this being indicated by the legend 60), the superposition of the mask on socket 1 brings holes 58 and 59 into alignment with the socket locating jacks G1 and G2, respectively. Then, when'the plug 2, oriented as in FIG. 2, is brought over the mask-andsocket combination, the pins G1 and G2 of the plug can pass through the mask holes 58 and 59 into the socket jacks G1 and G2, respectively. In this mask position, the socket jacks G3 and G4 are covered by the solid material of the mask. Of course, the pins A through Y of the plug 2 then pass through the mask aperture 57 into the jacks A through Y, respectively, of the socket 1.

When the mask 56 is turned over, so that its NC face is uppermost (as illustrated in FIG. 7, this being indicated by the legend 23), the superposition of the mask on socket 1 brings holes 58 and 59 into alignment with the socket locating jacks G3 and G4, respectively. Then, when the plug 2, oriented as in FIG. 3, is brought over the maskand-socket combination, the pins G1 and G2 of the plug can pass through the mask holes 58 and 59 into the socket jacks G3 and G4, respectively. In. this last-mentioned mask position, the socket jacks G1 and G2 are covered by the solid material of the mask. In this latter case, the pins A through Y of the plug 2 then pass through the mask aperture 57 into respective jacks of socket 1, but in a reverse order, pin A into jack Y, pin B into jack X, etc.; these connections are illustrated in FIG. 4b.

It is pointed out that rotation of the mask 56 through 180 from the NO position of FIG. 6, without turning it over, will bring it to the NC position of FIG. 7. Such a rotation could be employed, if desired; the legend 23 would then have to be relocated to correspond.

The invention claimed is:

1. A universal plug-in relay unit having a symmetrical multi-pin plug adapted to be inserted into a symmetrical multi-jack socket in one or the other of two alternative senses differentiated from each other by a relative plug rotation of 180, the two pins of said plug which alternatively enter the same jack of said socket constituting a pair of reciprocally related pins and said plug having a plurality of such pairs of reciprocally related pins; a relay in said unit connected to said plug and arranged for selective energization or deenergization in response to an abnormal condition, means including contacts controlled by said relay for establishing, after energization of said relay, a first current flow path between one pin of a first pair of reciprocally related pins and one pin of a second pair of reciprocally related pins; and means including other contacts controlled by said relay for establishing, after deenergization of said relay, a second current flow path between the other pin of said first pair of reciprocally related pins and the other pin of said second pair of reciprocally related pins.

2. Combination according to claim 1, wherein said first current flow path includes a diode in series with a pair of relay contacts closed by energization of said relay.

3. Combination according to claim 1, wherein said second current flow path includes a diode in series with a pair of relay contacts closed by deenergization of said relay.

4. Combination as defined in claim 1, wherein the socket jack entered alternatively by the two pins of said second pair of reciprocally related pins is connected to an alarm indicating device.

5. Combination as defined in claim 1, wherein the socket jack entered alternatively by the two pins of said first pair of reciprocally related pins is connected to a power source.

6. Combination in accordance with claim 1, including also another relay in said unit connected to said plug and arranged for manual release, said last-mentioned relay having contacts which are connected into each of said first and second current flow paths.

7. Combination as set forth in claim 6, wherein the contacts of the last-mentioned relay are closed by release thereof, and wherein such contacts are connected in series in each of said first and second current flow paths.

8. Combination in accordance with claim 1, including also means for establishing, upon energization of said relay, a third current flow path between said one pin of said first pair of reciprocally related pins and one pin of a third pair of reciprocally related pins, and means for establishing, upon deenergization of said relay, a fourth current flow path between the other pin of said first pair of reciprocally related pins and the other pin of said third pair of reciprocally related pins.

9. Combination as set forth in claim 8, including also another relay in said unit connected to said plug and arranged for manual release, said last-mentioned relay having contacts which are connected into said third current flow path and other contacts which are connected into said fourth current flow path.

10. Combination as described in claim 9, wherein the contacts of the last-mentioned relay are opened by release thereof, and wherein such contacts are connected in series in the respective third and fourth current flow paths.

11. Combination in accordance with claim 1, and in addition means including contacts controlled by said relay for establishing, upon energization of said relay, a fifth curret flow path between said other pin of said third pair of reciprocally related pins and said one pin of said second pair of reciprocally related pins, and means including contacts controlled by said relay for establishing, upon deenergization of said relay, a sixth current flow path between said one pin of said third pair of reciprocally related pins and said other pin of said second pair of reciprocally related pins.

12. Combination as set forth in claim 11, including also another relay in said unit connected to said plug and arranged for manual release, said last-mentioned relay having contacts which are connected into said fifth current flow path and other contacts which are connected into said sixth current flow path.

13. Combination as described in claim 12, wherein the contacts of the last-mentioned relay are opened by release thereof, and wherein such contacts are connected in series in the respective fifth and sixth current flow paths.

14. A universal plug-in relay unit having a symmetrical multi-pin plug adapted to be inserted into a symmetrical multi-jack socket in one or the other of two alternative senses differented from each other by a relative plug rotation of the two pins of said plug which alternatively enter the same jack of said socket constituting a pair of reciprocally related pins and said plug having a plurality of such pairs of reciprocally related pins; a relay in said unit connected to said plug and arranged for initial deenergization or energization in response to the application of power to said unit, means including contacts controlled by said relay for establishing, upon initial deenergization of said relay, a current flow path between one pin of a first path of reciprocally reated pins and one pin of a second pair of reciprocally related pins; and means including other contacts controlled by said relay l for establishing, upon initial energization of said relay; a current flow path between the other pin of said first pair of reciprocally related pins and, the other pin of said second pair of reciprocally related pins.

15. Combination as defined in claim 14, whereinthe socket jack entered alternatively by the two pins of said second pair of reciprocally related pins is connected to an alarm indicating device.

16. Combination as defined in claim 14, wherein the socket jack entered alternatively by the two pins of said first pair of reciprocally related pins is connected through a manually-operated switch to a power source.

v References Cited UNITED STATES PATENTS 2,227,970 1/1941 Hill 317-413 2,810,118 10/1957 Swan.

. FOREIGN PATENTS 845,077 7/1952 Germany.

' JOHN F. COUCH, Primary Examiner.

D. HARNISH, Assistant Examiner.

US. Cl. X.R. 317-137; 33918 

